chore: make pageTheme optional & provide default value

packages/theme/src/baseTheme.ts

@@ -23,6 +23,7 @@ import {
   BackstageThemeOptions,
   SimpleThemeOptions,
 } from './types';
+import { pageTheme as defaultPageThemes } from './pageTheme';
 
 const DEFAULT_FONT_FAMILY =
   '"Helvetica Neue", Helvetica, Roboto, Arial, sans-serif';
@@ -34,7 +35,7 @@ export function createThemeOptions(
     palette,
     fontFamily = DEFAULT_FONT_FAMILY,
     defaultPageTheme,
-    pageTheme,
+    pageTheme = defaultPageThemes,
   } = options;
 
   if (!pageTheme[defaultPageTheme]) {

packages/theme/src/types.ts

@@ -94,7 +94,7 @@ export interface BackstageThemeOptions extends ThemeOptions {
 export type SimpleThemeOptions = {
   palette: BackstagePaletteOptions;
   defaultPageTheme: string;
-  pageTheme: Record<string, PageTheme>;
+  pageTheme?: Record<string, PageTheme>;
   fontFamily?: string;
 };